PLANET software is a nutrient management decision support tool to help farmers and consultants with field level nutrient planning.
In order to reliably target fertiliser applications it is essential to know the soil status for individual fields through analysing your soil for pH, P, K & Mg.
If soils are high in phosphate (P2O5) or potash (K2O) then savings in fertiliser applications can be made. It is worth noting that target status for phosphate and potash are dependant upon the crop in rotation. For phosphate, soil type dictates the soils capacity to bind with applied phosphate see SRUC Technical Note 668 “Managing Soil Phosphorus” for more information. By identifying soil status through analysis, management practices can be tailored to build soil reserves up where levels are low or reduce fertiliser inputs where soil status is high.
On a farm in south east Scotland, soil analyses were taken in early 2016 and the results allowed for considerable savings in fertiliser applications. Most of the fields were either on or above target for phosphate and above target for potash. The farmer counted the number of trailer loads of pit silage being removed from each field. From this, an estimation was made on the weight of each trailer accounting for the dimensions of the trailer and the dry matter of the silage. Knowing yield allowed a calculation of crop offtake for phosphate and potash and using field level soil analysis, an account was made for the soil status. The organic manures on the farm were also analysed giving an indication of the nutrient content.
Taking one field as an example, it analysed moderate plus for phosphate and high for potash. In 2016 there were two applications of slurry before each of the two cuts and 556kg/ha of 24:4:14 was applied. For second cut
, 309kg/ha of 34.4N was applied. In comparison to 2017 where hen pen was applied pre first cut and slurry pre second cut, the nutrient budget calculation showed there was no requirement for any inorganic P & K. The only inorganic application was of bagged N where 346kg/ha of 34.4N was applied pre first cut and 309kg/ha pre second cut.
When nutrient budgeting it is important to make sure the crop offtake is being replaced, whether through managing high status soils, or through organic and inorganic applications. In 2016 the fertiliser cost was £1,948 on this field and in 2017 was £1,188 resulting in a saving of £760 or £75.40/ha. In order to continue to make savings whilst maintaining soil nutrient levels, a nutrient budget should be calculated for following years. Over the 12 fields (98.01ha) which the nutrient budget was calculated for a saving of £5,049 (£54.52/ha) was made. In 2016 the total fertiliser cost including spreading was £15,636 and in 2017 this was reduced to £10,587. This included a two cut silage system, spring barley and grazing.
As an added benefit of using software to create recommendations for fertilisers, many have the capacity to hold field records. Keeping fertiliser records is required for compliance under NVZ regulations but also for many crop assurance schemes. By using software to keep records it helps with fertiliser planning. For example if applying slightly more or less P or K in one year than is required, PLANET will carry this over to the following year by increasing or decreasing the starting balance. Therefor a running balance can quickly be observed by looking at individual fields and any over application, which leads to leaching and nutrient loss from your farm, can be avoided.
